100-490 · Question #22
Which IPv6 address is valid?
The correct answer is D. 2031:0:130F::9C0:876A:130B. An IPv6 address is represented as eight groups of four hexadecimal digits, each group representing 16 bits (two octets). The groups are separated by colons (:). An example of an IPv6 address is 2001:0db8:85a3:0000:0000:8a2e:0370:7334. The leading 0's in a group can be collapsed…
Question
Which IPv6 address is valid?
Options
- A2001:0db8:0000:130F:0000:0000:08GC:140B
- B2001:0db8:0:130H::87C:140B
- C2031::130F::9C0:876A:130B
- D2031:0:130F::9C0:876A:130B
How the community answered
(22 responses)- A14% (3)
- B5% (1)
- C9% (2)
- D73% (16)
Explanation
An IPv6 address is represented as eight groups of four hexadecimal digits, each group representing 16 bits (two octets). The groups are separated by colons (:). An example of an IPv6 address is 2001:0db8:85a3:0000:0000:8a2e:0370:7334. The leading 0's in a group can be collapsed using ::, but this can only be done once in an IP address.
Topics
Community Discussion
5
Anjali D.Oct 31, 2025D is the right call here. It uses valid hex digits throughout, the double colon appears only once to compress consecutive zero groups, and the overall structure stays within IPv6 rules, while A has an invalid "G" character, B has an invalid "H", and C uses the double colon twice which is not allowed.
Luis F.Nov 1, 2025Solid breakdown, and just to add a tiny bit of color, the reason only one double colon is allowed is that otherwise the parser cannot determine how many zero groups were omitted, making the address ambiguous.
Luis F.Nov 6, 2025Saw this exact type of question on my exam and I almost picked C until I remembered you can only use the double-colon compression once per address, so that knocked it out, then I spotted the "G" in A and the "H" in B which are not valid hex characters, and D was the only one left standing.
Viktor S.Nov 7, 2025Good elimination process, but make sure you actually understand why G and H fail, not just that they do, since "invalid hex character" needs to connect to the fact that hex only runs 0-9 and A-F, otherwise you are just memorizing symptoms instead of the rule.
Viktor S.Oct 15, 2025Took me a solid 30 seconds on the real exam because I almost marked C, forgetting that you can only use the double-colon compression once per address, not twice. D is clean: single ::, valid hex groups, no bogus characters like G or H that sneak into the wrong options to trip you up.